Plastic floating deck for storage tanks and method of construction thereof

ABSTRACT

A floating deck is constructed of a foamed plastic formed in place within a channelled rigid peripheral ring and is provided with elongated tension member carried by said ring and embedded in said plastic and also a reinforced sheet above and below which the plastic body is formed. Adjustable legs are provided to facilitate construction and repair.

United States Patent Inventors Walter E. Belanger Concord Turnpike, Lincoln; Donald T. Levitre, Chelsea, both of, Mass. 01773 Appl. No. 850,117

Filed Aug. 14, 1969 Patented June 8, 1971 Assignee said Walter E. Belanger, by said Donald T.

Levitre PLASTIC FLOATING DECK FOR STORAGE TANKS AND METHOD OF CONSTRUCTION THEREOF 7 Claims, 10 Drawing Figs.

US. Cl 220/26R, 220/268 Int. Cl 865d 87/18 Field of Search 220/26, 26 S, 26 SI, 26 D [56] References Cited UNITED STATES PATENTS 2,281,748 5/1942 Carney 220/26(S) 2,282,772 5 1942 Wiggins. 220/26 2,307,508 1/1943 Jayne 220/26(S) 2,586,856 2/1952 Orr et al. 220/26 3,079,029 2/1963 Moyer et al 220/26(S) 3,120,902 2/1964 Southworth et a1... 220/26(S) 3,158,667 11/1964 Michaels 220/26X 3,240,381 3/1966 Smith 220/26(S) FOREIGN PATENTS 815,105 6/1959 Great Britain 220/26 Primary Examiner.loseph R. Leclair Assistant Examiner-James R. Garrett Attorney-Russell & Nields ABSTRACT: A floating deck is constructed of a foamed plastic formed in place within a channelled rigid peripheral ring and is provided with elongated tension member carried by said ring and embedded in said plastic and also a reinforced sheet above and below which the plastic body is formed. Adjustable legs are provided to facilitate construction and repair.

PATENTEU JUN 8 I87! SHEET 1 OF 7 FIG. I

INVENTORS WALTER E. BELANGER DONALD T. LEVITRE WMJM ATTORNEYS PATENTEDJUN 8|97l 3588594 SHEET 2 [1F 7 FIG. 2

INVENTORS WALTER E. BELANGER DONALD T. LEVITRE MM/M ATTORNEYS PATENTEDJUN 8|97| 3 5 3 594 sum 3 OF 7 FIG. 3

INVENTORS WALTER E. BELANGER DONALD T. LEVITRE BY fiuWMM/Lz ATTORNEYS PATENTED JUN 8 I97! SHEET U 0F 7 FIG.

INVENTORS WALTER E BELANGEF DONALD T. LEVITRE ATTORNEYS PATENTED JUN 8 |97| sum 5 or 7 FIG. 6

INVENTORS WALTER E. BELANGER DONALD T. LEVITRE BY Mum ATTORNEYS PATENTEDJUN 8I9fl' 3583594 SHEET 7 OF 7 IINVENTORS WALTER E. BELANGER DONALD T. LEVITRE Mum ATTORNEYS PLASTIC FLOATING DECK FOR STORAGE TANKS AND METHOD OF CONSTRUCTION THEREOF BACKGROUND OF INVENTION l. Field of the Invention Volatile liquid storage vessels provided with floating cover decks to minimize evaporation of the stored liquid.

2. Description of the Prior Art It is generally recognized that it is desirable to cover a volatile liquid, such as gasoline, fuel oil and the like, which is contained within a storage tank, with a roof or deck which normally floats on the surface of said liquid and provides a virtually vaportight shield to cut down on the loss of such liquid by evaporation. Such decks have been made of lightweight metal structures, as for example in U.S. Pat. Nos. 3,l04,775 and 3,203,574. The use of a plastic foam blanket formed in place within a storage tank has been suggested, as for example in U.S. Pat. No. 3,158,667. Also, as indicated in U.S. Pat. No. 3,203,574, tanks of this kind must be cleaned periodically. Therefore, the floating deck structures should provide an arrangement where such cleaning may be carried out.

Prior art devices have been found to be deficient in that they are difficult to construct, involving considerable time and expense in their construction. Furthermore, the deck structures are quite fragile so that extreme care must be exercised by any workman venturing onto such structure either during its assembly or while engaged in cleaning or making repairs. Damages in the form of cracks or holes in the deck may easily occur and such damages are quite difficult to repair.

Summary ofthe Invention The present invention overcomes the difficulties and deflciencies of the prior art by providing a structure which can be constructed quickly and with a minimum of cost, is adaptable for installation in a wide variety of tank sizes with the maximum use of standardized parts, and which provides a monolithic plastic body having a high degree of rigidity and strength capable of supporting the weight of one or more workmen together with their equipment required for construction, repair and maintenance.

The floating deck, according to this invention, is constructed by assembling within the tank a rigid peripheral member having a channel shape. This peripheral member is supported by adjustable legs at a level above the bottom of the tank to provide adequate working space. Elongated tension members are stretched across the area surrounded by the peripheral member and secured to the peripheral member. A thin sheet of material is also stretched across said area above the tension members and secured to the peripheral member. A layer of plastic foam material such as urethane foam is sprayed onto said sheet and into the channel in said peripheral member above said sheet and is allowed to set into a hardened mass. Another layer of such plastic material is then sprayed upon the lower surface of said sheet, into said channel below said sheet and around said tension members to a depth sufficient to embed said tension members into the layer. Thereupon the lower layer is allowed to set into a hardened mass and additional tension is imparted to said tension members thus exerting compressive forces on said peripheral member and the plastic body. The result is a light, extremely strong deck body which safely supports the weight of workmen and equipment which may be required on the top of said deck during construction, maintenance, repair and cleaning.

Where the tank structure requires the deck to move along a vertical member mounted in the tank, such vertical member is also surrounded by a rigid channel member into which the plastic foam is also sprayed during construction. The provision of these several channel members results in a structure in which the upper and lower sides of the channel overlap the upper and lower surfaces of the plastic body which is locked and sealed into the channels giving added rigidity and strength to the deck. A relatively flexible sealing member is secured to the upper side ofeach channel to provide a sliding sealing contact with the respective adjacent vertical members and wall surfaces.

The upper surface of the hardened plastic deck is coated with a heat reflecting coating, such as an aluminum paint, to complement the heat insulating properties of the plastic material. The lower surface of the hardened plastic deck is coated with a tough abrasion resisting coating, such as an epoxy resin paint.

After the deck has been floated on the stored liquid, the legs are adjusted, by a workman walking on the top of the deck, to a minimum level, below that of the working level, at which the deck will rest when the stored liquid is drained from the tank.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a tank in which a floating deck according to the invention has been installed; portions being broken away in order to show the internal structure;

FIG. 2 is a plan view, with portions broken away, of the deck itself prior to the installation of a peripheral sealing ring;

FIG. 3 is an enlarged plan view of a portion of the deck structure located approximately at the area designated at 3 in FIG. 1;

FIG. 4 is a cross section along line M of FIG. 3;

FIG. 5 is a cross section along line 5-5 of FIG. 3;

FIG. 6 is a partial section representing the assembly of two portions of the peripheral supporting channel of the deck;

FIG. 7 is a partial plan view from below showing the structure for supporting and tensioning of a wire mesh sheet incorporated in the deck;

FIG. 8 is an enlarged section approximately along line 8-8 of FIG. 2;

FIG. 9 is a section along line 9-9 of FIG. 8; and

FIG. 10 is an enlarged section approximately along line 10-10 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to drawings, 11 represents a conventional, cylindrical, fluid storage tank, having a vertical cylindrical sidewall 12, a roof 13, supported by one or more columns 14, and a bottom wall 15. Within the tank 11 is constructed a floating deck 16 in accordance with the present invention.

The floating deck includes a rigid peripheral channel member 17 of suitable material, such as one-eighth inch thick sheet aluminum. As shown most clearly in FIGS. 4 and 5, this channel comprises a top wall member 18, a bottom wall member 19 and a sidewall member 20 extending below the bottom wall member to provide a vapor barrier skirt 21. The channel member is supplied in sections of convenient length which are bolted together in end to end relationship as shown in FIG. 6 by upper and lower splice plates 22 through which pass bolts 23. Preferably, each section of the channel member 17 forms a sufficiently small part of the total length of the peripheral member so that one standardized section length can be used to produce a rather wide variety of sizes of peripheral members.

Peripheral member 17 is provided with a plurality of appropriately spaced legs 24, the construction of which is most clearly shown in FIGS. 3 and 4. Each leg 24 comprises an outer tubular member 25 and inner tubular member 26 slida ble within member 25. Member 25 passes through the upper and lower wall members 18 and 19 of channel member 17 and is secured to said wall members by any suitable means such as welding. Tubular member 26 has a foot plate 27 secured to its lower end, which foot plate is adapted to rest on the bottom wall 15 of the tank II when the deck 16 is not floating on the stored liquid but is supported by legs 24 on said tank bottom. Foot plate 27 is provided with a drain hole 28, through which the stored liquid may flow. In order to support deck 16 at a minimum level above the tank bottom 15, for example, 3 feet, tubular member 26 has a plate 29 secured to it at a predetermined distance above foot plate 27. A pin 30, the function of which will be described below, is normally removed from its position as shown in FIG. 4. Therefore, when the liquid is drained from the tank, the deck drops until the lower end of tubular member rests on the plate 29 and supports the deck at the predetermined minimum level. A plate 31 is secured to the tubular member 26 and closes its upper end. Therefore, as the tank is filled with liquid and the deck floats on the liquid, tubular member 25 slides up along tubular member 26 until the upper end of tubular member 25 contacts plate 31 and lifts tubular member 26 with its foot plate 27 from the bottom wall 115.

In order to support the deck at a higher level, for example, 6 feet, to provide adequate working space during construction, cleaning and repair, tubular member 26 is provided with a transverse hole 32 spaced from foot plate 27 a distance which exceeds the desired working level support distance by approximately the thickness of the deck. Tubular member 25 is provided with a similar transverse hole 33. When holes 32 and 33 are in alignment, pin is adapted to be inserted through said holes to lock tubular members 25 and 26 together. ln this case, when the foot plate 27 is resting on the bottom wall 15, the deck will be supported at the desired working level. Since pin 30 is usually removed from the holes 32 and 33, it is provided with a retaining chain 34 fastened to any convenient adjacent portion of the structure. During the construction phase, pin 30 of each leg 24 is in place in holes 32 and 33 so that as the sections of peripheral member 17 are assembled, r ne m ber 17 will be erected and supported at the working level as described above.

To enable the deck to move vertically along support column 114 while maintaining a vapor sealaround such column, the deck structure is provided with a column negotiator 34 which is a ring-shaped device of a construction similar to that of peripheral member l7. Column negotiator 34 includes a top ring wall member 35, usually made of two halves bolted together by splice plates 36 and 37. Secured to wall member is a depending cylindrical skirt 38 which is adapted to dip into the liquid and form a vapor barrier. The upper portion of skirt 38 forms the backwall of a channel member, with member 35 as top wall, and a lower ring wall member 33 secured to skirt 38. When peripheral member 17 has been assembled adjacent sidewall 12 and column negotiator 34 has been assembled around column 14, a plurality of tension members 4t) are stretched across the intervening space between members R7 and 34. Each tension member is secured at one end to an eyebolt 411 passing through the sidewall 20 of peripheral member 17 and retained in place by a nut 42 whereby tension can be applied to the tension member 40. The other end of each tension member is secured to an eyebolt 43 passing through the skirt 38 of the column negotiator 34. Each eyebolt 43 is also provided with a nut 44 to retain it in place. When tension members have been placed in position, nuts 42 and 44 are tightened so as to impart sufficient tension to tension members 40 to support column negotiator at substantially the same level as peripheral member l7 and to provide a substantially flat horizontal web consisting of the tension members 40.

On top of the web of tension members 40 is laid a thin continuous sheet 45 of a material such as paper, cloth, plastic or the like. In order that the sheet 45 shall have the requisite strength, it is preferably backed or reinforced by a wire mesh 46. A preferred form of sheet 45 is paper backed by a 2-inch by 2-inch wire mesh 46. In order to hold the sheet 45 taut and flat, bolts 47 are provided in the sidewall 20 and cylindrical skirt 38 or members 17 and 34 respectively. Each bolt 47 has hooked end 48, as shown in FIG. 7, which hooks into the wire mesh 46. Each bolt 47 is also provided with a nut 49 whereby the hooks 43 may be tightened in the mesh 46 and exert sufficient tension on it to cause the sheet 45 to lie smooth and flat.

Where the distance spanned by the deck 16 is sufficiently great, it may be desirable to provide additional legs 24 at points intermediate the peripheral member 17 and the center of the deck. One of such intermediate legs is shown most clearly in FIG. 10. The structure ofthe leg 24 at this location is substantially identical with the leg structure as described above. While a channel member, such as that provided around the column negotiator 34, may be used at such intermediate leg, it is sufficient to faster a circular plate 50 to outer tubular member 25 at the point approximately where the lower surface of the deck is to be located. With the pin 30 inserted to hold the leg 24 at its construction level, each intermediate leg is set on its foot plate 27 at a desired location and passed through the sheet 45 and its wire mesh backing 46 which give to the leg 24 whatever slight additional lateral stability may be desired.

To provide passage through the deck 16, a man hole 51 is provided. it consists of a circular structure, substantially identical with that formed by the members 35 through 39 as shown in FIG. 8, and is provided with a manhole cover 52 secured to the member 35.

In some cases the deck to is provided with antirotational cables 53 fastened between the roof 13 and the bottom wall 15 of the tank 11. Each such cable 53 is also surrounded by a structure substantially identical with that surrounding the column 14 as shown in FIG. 8.

When each of the structures described above have been assembled in place, a layer 54 of plastic foam is sprayed onto the upper surface of sheet 45, filling that portion of each of the channel members lying above the sheet 45, and allowed to harden into a hard strong and relatively rigid layer. Sufficient plastic material is deposited to form a layer which, in a typical case may be about 2 inches thick. While polyurethane foam is the preferred material, other plastics, such as isophtalic polyesters and epoxies which may be sprayed and polymerized in place, can be used.

The spraying in place of the layer above the sheet 45 may be initiated by placing a few boards on one portion of the web formed by the tension member 40 and having a workman spray an adjacent segment of the layer in place. Within a comparatively few minutes the layers will harden sufficiently to support the workman who may then proceed onto such segment and complete the upper layer of plastic by progressively laying down successive segments.

After the plastic layer 54 has been completed, the workman may pass through the manhole 51 and spray an under layer 55 of plastic foam onto the lower surface of the sheet 45, filling the rest of each channel member and surrounding the wire mesh 46 and the tension members 40 to a depth, which in a typical case may be 1 inch. The resulting 3-inch thick plastic body has sufficient strength adequately to support workmen and equipment as may be required for maintenance, cleaning and repair.

When the upper and lower plastic layers 54 and 55 have set, additional strength, rigidity and stability is given to the structure by tightening the nuts 42 to increase the tension on the tension members 40 and to place both the peripheral member 17 and the body of the plastic deck under substantial compression.

The plastic body of the deck is an excellent heat insulator whereby it inhibits the flow of heat from the atmosphere above the deck into the stored liquid. Heating of the liquid would tend to increase loss of the liquid by evaporation. To inhibit the transfer of heat to the upper surface of the deck by radiation from the walls and roof of the tank, the upper surface of layer 54 may be coated with a heat reflecting layer 57 such as a layer of aluminum paint.

The inrush of liquid below the deck 16 during the filling of the tank exerts a substantial degree of abrasion to the deck. in order to resist such abrasion the lower surface of layer 50 may be coated with a tough abrasion resistant layer 58 such as a layer of epoxy resin paint.

in order to provide a vaportight seal between the peripheral number 17 and the sidewall 12, a relatively flexible sealing member such as a 2-inch thick strip of urethane 59 is bolted to the top of member l7. For this purpose the member i7 is provided with a series of bolts 60 each passing through the wall members 19 and 18 respectively and held in place by a nut 61. The sealing strip 59 is inserted over the upper ends of the bolts 60, a continuous metal channel 62 is placed on top of the sealing strip and held firmly in place by means of nuts 63 threaded onto the ends of bolts 60. The outer edges of strip slides along the wall 12 and maintains a vaportight wall as the deck 16 moves up and down.

To provide a seal around the column 14, the column negotiator 34 is also provided with a relatively flexible sealing sheet 64, also preferably of urethane and is bolted or riveted in place by means of a metal strip 65 held in place by bolts or rivets 66. It is to be understood that the antirotational cables 53 are also provided with such sealing sheets.

When the structure has been completed, liquid is pumped into the tank through a suitable pipe. As the level of the liquid rises, the deck 16 will float on the surface of the liquid and raise the legs 24 so that the foot plates 27 are raised from the bottom wall 15. Thereupon, a workman may proceed into the upper surface of the deck 16 and pull the pins 30 from the legs 24 permitting the inner tubular member 26 to drop with their plates 31 closing the upper ends of outer tubular member 25. The structure is now in such condition that when the liquid is drawn from the tank, the deck 16 will drop until it is supported at the minimum 3-foot level. When however it is desired to do work below the deck 16, a workman will proceed onto the deck 16 before the liquid is drained below the 6-foot level, and will pull up each plate 31 and insert the pins 30 when the holes 32 and 33 are in alignment. Thereupon the structure is in condition so that the deck will be supported at the 6-foot working level even when all the liquid is drained from the tank.

The novel structure as described above is light, strong, and inexpensive to install and maintain. lt is highly resistant to damage. Should any cracks tend to form in the layers 54 or 55, such cracks do not progress beyond the sheet 45 with its backing mesh 46, thus preserving the vaportight integrity of the deck. Such cracks are also easily repaired by spraying plastic into them. Other advantages of this structure will become apparent to its users.

We claim:

1. A floating deck of plastic material for a volatile liquids storage vessel having an upstanding peripheral wall, wherein the deck comprises: (a) a rigid peripheral member surrounding substantially the entire cross-sectional area within said wall; (b) elongated tension members connected to said peripheral member and extending across the span ofsaid deck within said peripheral member; (c) a body of plastic material embedding and filling the voids around said tension members, in sealing contact with said peripheral member, and covering substantially the entire area surrounded by said peripheral member; (d) said peripheral member being of sufficient rigidity to maintain said tension member under substantial tension within said body so as to impart substantial weight bearing strength in a direction normal to the principal plane of said body.

2. A deck as specified in claim 1 in which (a) said deck has secured thereto a plurality of legs, each of said legs being adjustable to a lower position at which said deck is supported at a minimum height above the bottom of the vessel as liquid is drained therefrom, each of said legs also being adjustable to a higher position at which said legs also being adjustable to a higher position at which said deck is supported at sufficient distance above the bottom of said vessel as liquid is drained therefrom to provide adequate working space for a workman below said deck; (b) said weight bearing strength being sufficient to support the weight of said workman on the upper surface of said body; and (c) a passageway through said body to enable said workman to pass through said body.

3. A deck as specified in claim 1 in which said tension members are in sufficiently high tension to impart substantial radial compression to said plastic body.

4. A deck as specified in claim 1 in which (a) a thin sheet of material is located above said tension members covering substantially the entire area surrounded by said peripheral member, and (b) the plastic material is located both above and below said sheet so that said tension members and said sheet are embedded in said body of plastic material:

5. A deck as specified in claim 4 in which said sheet is supported in tension from said peripheral member.

6. A deck as specified in claim 5 in which said sheet is backed by a wire mesh secured thereto:

7. A deck as specified in claim Sin which said tension members are in sufficiently high tension to impart substantial radial compression to said plastic body. 

1. A floating deck of plastic material for a volatile liquids storage vessel having an upstanding peripheral wall, wherein the deck comprises: (a) a rigid pEripheral member surrounding substantially the entire cross-sectional area within said wall; (b) elongated tension members connected to said peripheral member and extending across the span of said deck within said peripheral member; (c) a body of plastic material embedding and filling the voids around said tension members, in sealing contact with said peripheral member, and covering substantially the entire area surrounded by said peripheral member; (d) said peripheral member being of sufficient rigidity to maintain said tension member under substantial tension within said body so as to impart substantial weight bearing strength in a direction normal to the principal plane of said body.
 2. A deck as specified in claim 1 in which (a) said deck has secured thereto a plurality of legs, each of said legs being adjustable to a lower position at which said deck is supported at a minimum height above the bottom of the vessel as liquid is drained therefrom, each of said legs also being adjustable to a higher position at which said legs also being adjustable to a higher position at which said deck is supported at sufficient distance above the bottom of said vessel as liquid is drained therefrom to provide adequate working space for a workman below said deck; (b) said weight bearing strength being sufficient to support the weight of said workman on the upper surface of said body; and (c) a passageway through said body to enable said workman to pass through said body.
 3. A deck as specified in claim 1 in which said tension members are in sufficiently high tension to impart substantial radial compression to said plastic body.
 4. A deck as specified in claim 1 in which (a) a thin sheet of material is located above said tension members covering substantially the entire area surrounded by said peripheral member, and (b) the plastic material is located both above and below said sheet so that said tension members and said sheet are embedded in said body of plastic material:
 5. A deck as specified in claim 4 in which said sheet is supported in tension from said peripheral member.
 6. A deck as specified in claim 5 in which said sheet is backed by a wire mesh secured thereto:
 7. A deck as specified in claim 5 in which said tension members are in sufficiently high tension to impart substantial radial compression to said plastic body. 